1. Field of the Invention
The present invention generally relates to an antenna device.
2. Description of the Related Art
An example of an antenna device of a monopole type is used for data communication in a small-sized electronic communication apparatus such as a personal computer, a mobile phone and an audiovisual apparatus because the length of an antenna element of a monopole-type antenna is about one fourth (¼) of the wavelength λ of a using frequency.
An antenna device which performs high-capacity communication is used for BLUETOOTH (BLUETOOTH is a registered trademark) in a 2.4 GHz band which is standardized as IEEE 802.15.1, a wireless Local Area Network (LAN) which is standardized as IEEE 802.11, and so on.
Along with recent increases of communication information amount, Patent Documents 1 and 2 provide antennas for attaining miniaturization and a broadband property.
A sufficient radiant gain (antenna gain) is not obtainable if the monopole type antenna device is merely miniaturized.
The object of the present invention is to provide an antenna device in which the miniaturization and the increase of the radiant gain are achieved.
[Patent Document 1] Japanese Laid-open Patent Publication No. 2007-060386
[Patent Document 2] Japanese Laid-open Patent Publication No. 2003-101326